This invention relates to a family of related crystalline aluminosilicate zeolites examples of which have been designated UZM-5, UZM-5P and UZM-6. These compositions are structurally different from other zeolites and can catalyze various hydrocarbon processes.
Zeolites are crystalline aluminosilicate compositions which are microporous and which have a three-dimensional oxide framework formed from corner sharing AlO2 and SiO2 tetrahedra. Numerous zeolites, both naturally occurring and synthetically prepared are used in various industrial processes. Zeolites are characterized by having pore openings of uniform dimensions, having a significant ion exchange capacity, and being capable of reversibly desorbing an adsorbed phase which is dispersed throughout the internal voids of the crystal without significantly displacing any atoms which make up the permanent zeolite crystal structure.
The number of synthetic zeolites is well over a hundred as evidenced by the Atlas of Zeolite Structure Types published by the International Zeolite Association (IZA). As is well known, zeolites are distinguished from each other on the basis of their composition, crystal structure and adsorption properties. One method commonly used in the art to distinguish zeolites is x-ray diffraction.
Applicants have synthesized a family of crystalline zeolitic compositions which have unique x-ray diffraction patterns and have an empirical formula on an anhydrous basis in terms of molar ratios of:
Mmn+Rrp+Al(1xe2x88x92x)ExSiyOz
where M is at least one exchangeable cation selected from the group consisting of alkali and alkaline earth metals, xe2x80x9cmxe2x80x9d is the mole ratio of M to (Al+E) and varies from about 0 to about 1.2, R is a nitrogen-containing organic cation selected from the group consisting of quaternary ammonium ions, protonated amines, protonated diamines, protonated alkanolamines, quaternary alkanolammonium ions, diquaternary ammonium ions, and mixtures thereof, xe2x80x9crxe2x80x9d is the mole ratio of R to (Al+E) and has a value of about 0.25 to about 3.0, E is an element selected from the group consisting of Ga, Fe, In, Cr, and B, xe2x80x9cxxe2x80x9d is the mole fraction of E and varies from 0 to about 0.5, xe2x80x9cnxe2x80x9d is the weighted average valence of M and has a value of +1 to about +2, xe2x80x9cpxe2x80x9d is the weighted average valence of R and has a value of +1 to about +2, xe2x80x9cyxe2x80x9d is the mole ratio of Si to (Al+E) and varies from about 5 to about 12, and xe2x80x9czxe2x80x9d is the mole ratio of O to (Al+E) and has a value determined by the equation:
z=(mxc2x7n+rxc2x7p+3+4xc2x7y)/2
Specific members of this family of zeolites are: UZM-5, UZM-5P and UZM-6. These zeolites can catalyze various hydrocarbon conversion processes such as alkylation of benzene and isomerization of xylene.
This invention relates to a new family of zeolite, a process for preparing the zeolites and a process using the zeolites. Accordingly, one embodiment of the invention is a microporous crystalline zeolite having a composition in the as synthesized form in terms of mole ratios of the elements given by
Mmn+Rrp+Al(1xe2x88x92x)ExSiyOz
where M is at least one exchangeable cation selected from the group consisting of alkali and alkaline earth metals, xe2x80x9cmxe2x80x9d is the mole ratio of M to (Al+E) and varies from about 0 to about 1.2, R is a nitrogen-containing organic cation selected from the group consisting of protonated amines, protonated diamines, protonated alkanolamines, quaternary ammonium ions, diquaternaryammonium ions, quaternized alkanolamines and mixtures thereof, xe2x80x9crxe2x80x9d is the mole ratio of R to (Al+E) and has a value of about 0.25 to about 3.0, E is an element selected from the group consisting of Ga, Fe, In, Cr, B, and mixtures thereof xe2x80x9cxxe2x80x9d is the mole fraction of E and varies from 0 to 0.5, xe2x80x9cnxe2x80x9d is the weighted average valence of M and has a value of about +1 to about +2, xe2x80x9cpxe2x80x9d is the weighted average valence of R and has a value of +1 to about +2, xe2x80x9cyxe2x80x9d is the mole ratio of Si to (Al+E) and varies from about 5 to about 12 and xe2x80x9czxe2x80x9d is the mole ratio of 0 to (Al+E) and has a value determined by the equation:
z=(mxc2x7n+rxc2x7p+3+4xc2x7y)/2
the material characterized in that it has at least two x-ray diffraction peaks, one at a d-spacing of 3.9xc2x10.12 xc3x85 and one at 8.6xc2x10.20 xc3x85.
In a particular embodiment, the zeolite is designated UZM-5 and has the diffraction pattern having at least the d-spacings and intensities set forth in Table A:
Another embodiment of the invention is a process for preparing the above-described zeolites which comprises forming a reaction mixture containing reactive sources of R, Al, Si and optionally E and/or M and heating the reaction mixture at a temperature of about 100xc2x0 C. to about 175xc2x0 C., the reaction mixture having a composition expressed in terms of mole ratios of the oxides of:
aM2/nO:bR2/pO:(1xe2x88x92c)Al2O3:cE2O3:dSiO2:eH2O
where xe2x80x9caxe2x80x9d has a value of about 0 to about 2.0, xe2x80x9cbxe2x80x9d has a value of about 1.5 to about 30, xe2x80x9ccxe2x80x9d has a value of about 0 to about 0.5, xe2x80x9cdxe2x80x9d has a value of 5 to about 30, and xe2x80x9cexe2x80x9d has a value of about 30 to about 6000.
Yet another embodiment of the invention is a hydrocarbon conversion process using the above-described zeolites. More specifically the hydrocarbon conversion process is the alkylation of benzene with an olefin or the isomerization of xylenes.
These and other objects and embodiments will become more apparent after the following detailed description of the invention.
Applicants have synthesized a new family of zeolites. In its as-synthesized form, this family of zeolites has a composition on an anhydrous basis that is represented by the formula:
Mmn+Rrp+Al(1xe2x88x92x)ExSiyOz
M is an exchangeable cation and is selected from the group consisting of alkali and alkaline earth metals. Specific examples of the M cations include but are not limited to lithium, sodium, potassium, cesium, strontium, calcium, magnesium, barium and mixtures thereof. The value of xe2x80x9cmxe2x80x9d which is the mole ratio of M to (Al+E) varies from 0 to about 1.2. R is a nitrogen containing organic cation and is selected from the group consisting of protonated amines, protonated diamines, protonated alkanolamines, quaternary ammonium ions, diquaternary ammonium ions, quaternized alkanolammonium ions and mixtures thereof. The value of xe2x80x9crxe2x80x9d which is the mole ratio of R to (Al+E) varies from about 0.25 to about 3.0. The value of xe2x80x9cnxe2x80x9d which is the weighted average valence of M varies from +1 to about +2. The value of xe2x80x9cpxe2x80x9d, which is the average weighted valence of the organic cation has a value from about +1 to about +2. E is an element which is present in the framework and is selected from the group consisting of gallium, iron, boron chromium, indium and mixtures thereof. The value of xe2x80x9cxxe2x80x9d which is the mole fraction of E varies from 0 to about 0.5. The ratio of silicon to (Al+E) is represented by xe2x80x9cyxe2x80x9d which varies from about 5 to about 12, while the mole ratio of O to (Al+E) is represented by xe2x80x9czxe2x80x9d and xe2x80x9d has a value given by the equation:
z=(mxc2x7n+rxc2x7p+3+4xc2x7y)/2
When M is only one metal, then the weighted average valence is the valence of that one metal, i.e. +1 or +2. However, when more than one M metal is present, the total amount of:       M    m          n      +        =            M      m1                        (          n1          )                +              +          M      m2                        (          n2          )                +              +          M      m3                        (          n3          )                +              +    …  
and the weighted average valence xe2x80x9cnxe2x80x9d is given by the equation:   n  =                              m          1                ·                  n          1                    +                        m          2                ·                  n          2                    +                        m          3                ·                  n          3                    +      ⋯                      m        1            +              m        2            +                        m          3                ⁢                  xe2x80x83                ⁢        ⋯            
Similarly when only one R organic cation is present, the weighted average valence is the valence of the single R cation, i.e., +1 or +2. When more than one R cation is present, the total amount of R is given by the equation:
Rrp+=Rr1(p1)++Rr2(p2)++Rr3(p3)+
and the weighted average valence xe2x80x9cpxe2x80x9d is given by the equation:   p  =                                          p            1                    ·                      r            1                          +                              p            2                    ·                      r            2                          +                              p            3                    ·                      r            3                          +        ⋯                              r          1                +                  r          2                +                  r          3                +        ⋯              .  
These aluminosilicate zeolites, are prepared by a hydrothermal crystallization of a reaction mixture prepared by combining reactive sources of R, aluminum, optionally E and/or M and silicon in aqueous media. Accordingly, the aluminum sources include, but are not limited to, aluminum alkoxides, precipitated alumina, aluminum hydroxide, aluminum salts and aluminum metal. Specific examples of aluminum alkoxides include, but are not limited to aluminum orthosec-butoxide, and aluminum orthoisopropoxide. Sources of silica include but are not limited to tetraethylorthosilicate, fumed silicas, precipitated silicas and colloidal silica. Sources of the M metals include but are not limited to the halide salts, nitrate salts, acetate salts, and hydroxides of the respective alkali or alkaline earth metals. Sources of the E elements include but are not limited to alkali borates, boric acid, precipitated gallium oxyhydroxide, gallium sulfate, ferric sulfate, ferric chloride, chromium chloride, chromium nitrate, indium chloride and indium nitrate. When R is a quaternary ammonium cation, the sources include without limitation the hydroxide, and halide compounds. Specific examples include without limitation tetramethylammonium hydroxide, tetraethylammonium hydroxide, hexamethonium bromide, tetramethylammonium chloride, methyltriethylammonium hydroxide. R may also be neutral amines, diamines, and alkanolamines. Specific examples are triethanolamine, triethylamine, and N,N,Nxe2x80x2,Nxe2x80x2 tetramethyl-1,6-hexanediamine.
The reaction mixture containing reactive sources of the desired components can be described in terms of molar ratios of the oxides by the formula:
aM2/nO:bR2/pO:(1xe2x88x92c)Al2O3:cE2O3:dSiO2:eH2O
where xe2x80x9caxe2x80x9d is the mole ratio of the oxide of M and has a value of 0 to about 2, xe2x80x9cbxe2x80x9d is the mole ratio of the oxide of R and has a value of about 1.5 to about 30, xe2x80x9cdxe2x80x9d is the mole ratio of silica and has a value of about 5 to about 30, xe2x80x9ccxe2x80x9d is the mole ratio of the oxide of E and has a value from 0 to about 0.5, and xe2x80x9cexe2x80x9d is the mole ratio of water and has a value of about 30 to about 6000. The reaction mixture is now reacted at reaction conditions including a temperature of about 100xc2x0 C. to about 175xc2x0 C. and preferably from about 140xc2x0 C. to about 160xc2x0 C. for a period of about 12 hours to about 14 days and preferably for a time of about 2 days to about 5 days in a sealed reaction vessel under autogenous pressure. After crystallization is complete, the solid product is isolated from the heterogeneous mixture by means such as filtration or centrifugation, and then washed with de-ionized water and dried in air at ambient temperature up to about 100xc2x0 C.
As synthesized, the zeolites will contain some of the exchangeable or charge balancing cations in its pores. These exchangeable cations can be exchanged for other cations, or in the case of organic cations, they can be removed by heating under controlled conditions. All of these methods are well known in the art.
The crystalline zeolites are characterized by a three-dimensional framework structure of at least SiO2 and AlO2 tetrahedral units. These zeolites are further characterized by their unique x-ray diffraction pattern. The x-ray diffraction pattern has at least two peaks: one peak at a d-spacing of about 3.9xc2x10.12 xc3x85 and one peak at a d-spacing of about 8.6xc2x10.20 xc3x85. To allow for ready reference, the different structure types and compositions of crystalline zeolites have been given arbitrary designation of UZM-h, where xe2x80x9chxe2x80x9d is an integer starting at one and where for example xe2x80x9c1xe2x80x9d represents a framework of structure type xe2x80x9c1xe2x80x9d. That is one or more zeolitic composition with different empirical formulas can have the same structure type xe2x80x9chxe2x80x9d, e.g. xe2x80x9c1xe2x80x9d.
In this respect, the following species can be identified by their x-ray diffraction patterns which have at least the d-spacing and relative intensities set forth in Tables A to C.
The zeolites of this invention are capable of separating mixtures of molecular species based on the molecular size (kinetic diameter) or on the degree of polarity of the molecular species. When the separation of molecular species is based on molecular size, separation is accomplished by the smaller molecular species entering the intracrystalline void space while excluding larger species. The kinetic diameters of various molecules such as oxygen, nitrogen, carbon dioxide, carbon monoxide are provided in D. W. Breck, Zeolite Molecular Sieves, John Wiley and Sons (1974) p. 636.
The crystalline microporous compositions of the present invention either as synthesized or after calcination can be used as catalysts or catalyst supports in hydrocarbon conversion processes. Hydrocarbon conversion processes are well known in the art and include cracking, hydrocracking, alkylation of both aromatics and isoparaffins, isomerization, polymerization, reforming, dewaxing, hydrogenation, dehydrogenation, transalkylation, dealkylation, hydration, dehydration, hydrotreating, hydrodenitrogenation, hydrodesulfurization, methanation and syngas shift process. Specific reaction conditions and the types of feeds which can be used in these processes are set forth in U.S. Pat. Nos. 4,310,440 and 4,440,871 which are incorporated by reference. Preferred hydrocarbon conversion processes are alkylation of aromatics and isomerization of xylenes.
Other reactions may be catalyzed by these crystalline microporous compositions, including base-catalyzed side chain alkylation of alkylaromatics, aldol-condensations, olefin double bond isomerization and isomerization of acetylenes, alcohol dehydrogenation, and olefin dimerization, oligomerization and conversion of alcohol to olefins. Suitably ion exchanged forms of these materials can catalyze the reduction of NOx to N2 in automotive and industrial exhaust streams. Some of the reaction conditions and types of feeds that can be used in these processes are set forth in U.S. Pat. No. 5,015,796 and in H. Pines, THE CHEMISTRY OF CATALYTIC HYDROCARBON CONVERSIONS, Academic Press (1981) pp. 123-154 and references contained therein, which are incorporated by reference.
The X-ray patterns presented in the following examples (and tables above) were obtained using standard X-ray powder diffraction techniques. The radiation source was a high-intensity X-ray tube operated at 45 kV and 35 ma. The diffraction pattern from the copper K-alpha radiation was obtained by appropriate computer based techniques. Flat compressed powder samples were continuously scanned at 2xc2x0 (2xcex8) per minute from 2xc2x0 to 70xc2x0(2xcex8). Interplanar spacings (d) in Angstrom units were obtained from the position of the diffraction peaks expressed as 2xcex8 where xcex8 is the Bragg angle as observed from digitized data. Intensities were determined from the integrated area of diffraction peaks after subtracting background, xe2x80x9cIoxe2x80x9d being the intensity of the strongest line or peak, and xe2x80x9cIxe2x80x9d being the intensity of each of the other peaks.
As will be understood by those skilled in the art, the determination of the parameter 2xcex8 is subject to both human and mechanical error, which in combination can impose an uncertainty of about xc2x10.4 on each reported value of 2xcex8 and up to xc2x10.5 on reported values for nanocrystalline materials. This uncertainty is, of course, also manifested in the reported values of the d-spacings, which are calculated from the xcex8 values. This imprecision is general throughout the art and is not sufficient to preclude the differentiation of the present crystalline materials from each other and from the compositions of the prior art. In some of the X-ray patterns reported, the relative intensities of the d-spacings are indicated by the notations vs, s, m and w which represent very strong, strong, medium, and weak, respectively. In terms of 100xc3x97I/Io, the above designations are defined as w=0-15; m=15-60; s=60-80 and vs=80-100. In certain instances the purity of a synthesized product may be assessed with reference to its X-ray powder diffraction pattern. Thus, for example, if a sample is stated to be pure, it is intended only that the X-ray pattern of the sample is free of lines attributable to crystalline impurities, not that there are no amorphous materials present.
In order to more fully illustrate the invention, the following examples are set forth. It is to be understood that the examples are only by way of illustration and are not intended as an undue limitation on the broad scope of the invention as set forth in the appended claims.